High-density Lipoprotein Cholesterol In Humans Research Articles

Ethanol-mediated upregulation of APOA1 gene expression in HepG2 cells is independent of de novo lipid biosynthesis

BackgroundModerate alcohol intake in human increases HDL-cholesterol, and has protective effects against cardiovascular disease (CVD). Although de novo lipid synthesis inhibitors are highly effective in lowering total and LDL-cholesterol they have only modest effects on raising HDL-C. A better understanding of the mechanism of ethanol-mediated HDL-C regulation could suggest new therapeutic approaches for CVD.MethodsHuman hepatoblastoma (HepG2) and colorectal epithelial adenocarcinoma (Caco-2) cells were incubated in the presence of varying concentrations of ethanol in the culture medium, with or without addition of de novo lipid synthesis (DNLS) inhibitors (atorvastatin and/or TOFA). ApoA1 protein was measured by Western blot, and RNA of lipid pathway genes APOA1, APOC3, APOA4, APOB100, HMGCR, LDLR, and SREBF2 by quantitative RT-PCR. Lipoproteins (VLDL, LDL, and HDL) and lipids were also monitored.ResultsEthanol stimulated ApoA1 protein (both cytoplasmic and secreted) and APOA1 RNA levels in HepG2 cells in a dose sensitive way, with ~ 50% upregulation at 100 mM ethanol in the medium. The effect was not observed in intestinal-derived Caco-2 cells. DNLS inhibitors did not block the upregulation of ApoA1 RNA by ethanol; TOFA alone produced a modest increase in ApoA1 RNA. Ethanol had no effect on ABCA1 protein levels. Addition of ethanol to the cell medium led to modest increases in de novo synthesis of total cholesterol, cholesteryl esters and triglycerides, and as expected these increases were blocked when the lipid synthesis inhibitors were added. Ethanol stimulated a small increase in HDL and VLDL but not LDL synthesis. Ethanol in the cell medium also induced modest but measurable increases in the RNA of APOC3, APOA4, APOB, LDLR, and HMGCR genes. Unlike APOA1, induction of RNA from APOC3 and APOA4 was also observed in Caco-2 cells as well as HepG2 cells.ConclusionThis study has verified the previously reported upregulation of APOA1 by exposure of HepG2, but not Caco-2 cells, to ethanol in the culture medium. It is shown for the first time that the effect is dependent on RNA polymerase II-mediated transcription, but not on de novo biosynthesis of cholesterol or fatty acids, and therefore is not a generalized metabolic response to ethanol exposure. Some other lipid pathway genes are also modulated by ethanol exposure of cells. The results reported here suggest that the proximal signaling molecule leading to increased APOA1 gene expression in response to ethanol exposure may be free acetate or acetyl-CoA.Take homeUpregulation of ApoA1 gene expression in hepatoma cells in culture, upon exposure to moderate ethanol concentrations in the medium, occurs at the level of RNA and is not dependent on new cholesterol or fatty acid synthesis. The primary signaling molecule may be free acetate or acetyl-CoA. These results are important for understanding the mechanism by which moderate alcohol consumption leads to upregulation of serum HDL-cholesterol in humans, and suggests new approaches to targeting HDL as a risk factor for cardiovascular disease.

Effect of tomato consumption on fasting blood glucose and lipid profiles: A systematic review and meta‐analysis of randomized controlled trials

Tomato (Solanum lycopersicum) phytochemicals, which include phytoene, phytofluene, beta-carotene, flavonoids, lycopene, and polyphenols, have been shown to improve the effects of fasting on plasma triglyceride (TG), low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), total cholesterol (TC), and fasting blood sugar (FBS). The aim of this study was to systematically evaluate the effects of Tomato TC, TG, HDL, LDL, and FBS in humans. A systematic literature search was conducted in PubMed/MEDLINE, Web of sciences, and SCOPUS databases by two researchers for studies published until August of 2019 without language and time limitations. Results were combined with random effect models. Six studies were included in this meta-analysis. Combined results reveal a significant reduction in cholesterol (weighted mean difference [WMD]: -4.39 mg/dl, 95% CI: -7.09, -1.68, I2 = % 48, p heterogeneity: .05), TG (WMD: -3.94 mg/dl, 95% CI: -7.67, -0.21, I2 = % 90, p heterogeneity: .001), LDL levels (WMD: -2.09 mg/dl, 95% CI: -3.73, -0.81, I2 = % 78, p heterogeneity: .001), and increasing in HDL levels (WMD: 2.25 mg/dl, 95% CI: 0.41, 4.10, I2 = % 97, p heterogeneity: .001). Tomato was found to have a higher reduction effect on TG and LDL in younger participants. While pooled results indicate no significant effect on FBS levels (WMD: 0.59 mg/dl, 95% CI: -0.28, 1.46, I2 = % 95, p heterogeneity: .001). In conclusion, the results indicate a significant reduction in total cholesterol, TG, and LDL and increase in HDL levels that is caused by tomato consumption.

Multiplexed Targeted Resequencing Identifies Coding and Regulatory Variation Underlying Phenotypic Extremes of High-Density Lipoprotein Cholesterol in Humans.

Genome-wide association studies have uncovered common variants at many loci influencing human complex traits, such as high-density lipoprotein cholesterol (HDL-C). However, the contribution of the identified genes is difficult to ascertain from current efforts interrogating common variants with small effects. Thus, there is a pressing need for scalable, cost-effective strategies for uncovering causal variants, many of which may be rare and noncoding. Here, we used a molecular inversion probe target capture approach to resequence both coding and regulatory regions at 7 HDL-C-associated loci in 797 individuals with extremely high HDL-C versus 735 low-to-normal HDL-C controls. Our targets included protein-coding regions of GALNT2, APOA5, APOC3, SCARB1, CCDC92, ZNF664, CETP, and LIPG (>9 kb) and proximate noncoding regulatory features (>42 kb). Exome-wide genotyping in 1114 of the 1532 participants yielded a >90% genotyping concordance rate with molecular inversion probe-identified variants in ≈90% of participants. This approach rediscovered nearly all established genome-wide association studies associations in GALNT2, CETP, and LIPG loci with significant and concordant associations with HDL-C from our phenotypic extremes design at 0.1% of the sample size of lipid genome-wide association studies. In addition, we identified a novel, rare, CETP noncoding variant enriched in the extreme high HDL-C group (P<0.01, score test). Our targeted resequencing of individuals at the HDL-C phenotypic extremes offers a novel, efficient, and cost-effective approach for identifying rare coding and noncoding variation differences in extreme phenotypes and supports the rationale for applying this methodology to uncover rare variation-particularly noncoding variation-underlying myriad complex traits.

Adjustment of nonconfounding covariates in case-control genetic association studies

It has recently been reported that adjustment of nonconfounding covariates in case-control genetic association analyses may lead to decreased power when the phenotype is rare. This observation contrasts a well-known result for clinical trials where adjustment of baseline variables always leads to increased power for testing randomized treatment effects. In this paper, we propose a unified solution that guarantees increased power through covariate adjustment regardless of whether the phenotype is rare or common. Our method exploits external phenotype prevalence data through a profile likelihood function, and can be applied to fit any commonly used penetrance models including the logistic and probit regression models. Through extensive simulation studies, we showed empirically that the power of our method was indeed higher than available analysis strategies with or without covariate adjustment, and can be considerably higher when the phenotype was common and the covariate effect was strong. We applied the proposed method to analyze a case-control genetic association study on human high density lipoprotein cholesterol level.

High-Density Lipoprotein Function in Cardiovascular Disease and Diabetes Mellitus.

Cardiovascular disease (CVD) is the most common cause of death worldwide.1 Major CVD risk factors are hypertension, smoking, physical inactivity, abnormal glucose levels/diabetes mellitus, and dyslipidemia. Among these, dyslipidemia characterized by a low level of HDL-C (high-density lipoprotein cholesterol) is strongly and inversely correlated with CVD risk,2–4 and low HDL-C levels is part of the atherogenic dyslipidemia complex associated with diabetes mellitus.5 These observations triggered intense interest in increasing HDL-C levels for therapeutic intervention of CVD.6,7 However, several recent lines of evidence now suggest that the association between HDL-C levels and CVD status may be indirect or more complicated than previously recognized.7 Thus, human genetic studies demonstrate that genetically altered HDL-C levels do not necessarily translate to an altered risk of CVD.8–12 Phase III clinical trials of drugs that elevate HDL-C, such as niacin and CETP (cholesteryl ester transfer protein) inhibitors, also have largely failed to reduce CVD events in statin-treated subjects with established CVD.13–15 For several CETP inhibitors, improvement in CVD prevention was unsuccessful because of off-target effects (torcetrapib) or lack of efficacy (dalcetrapib and evacetrapib).14,16–18 The exception is the recent REVEAL trial (Randomized Evaluation of the Effects of Anacetrapib Through Lipid-Modification), which included more subjects and was performed for longer than previous CETP inhibitor trials. The REVEAL demonstrated that the CETP inhibitor anacetrapib exhibited beneficial effects on cardiovascular outcomes on top of those of statin therapy, although the risk reduction was moderate19,20 and might have been due, at least in part, to a reduction in non-HDL-C rather than elevated HDL-C.21 Considering these cumulative observations, it remains uncertain whether increased HDL-C directly impacts atherosclerosis and the …

Novel regulators of plasma lipid levels.

To highlight very recent studies identifying novel regulatory molecules and mechanisms in plasma lipid metabolism. Two novel regulatory mechanisms of LDL receptor (LDLR) intracellular trafficking have been described. The "COMMD/CCDC22/CCDC93" and "Wiskott-Aldrich syndrome protein and SCAR homologue" complexes were found to be involved in LDLR endosomal sorting and recycling, whereas the GRP94 was shown to protect LDLR from early degradation within the hepatocyte secretory pathway. Additionally, the transcription factors PHD1 and Bmal1 were identified to regulate LDL-C levels in mice by modulating cholesterol excretion. Important advances are reported on the relevance of two Genome Wide Association Studies hits: Reassessment of GALNT2 showed, in contrast to previous reports, that loss of GALNT2 reduces HDL-cholesterol in humans and other mammalian species, while phospholipid transfer protein was identified as an additional target of GALNT2. Tetratricopeptide repeat domain protein 39B was found to promote ubiquitination and degradation of Liver X receptor, and its deficiency increased HDL-cholesterol and cholesterol removal while also inhibiting lipogenesis in mice. The unraveling of mechanisms how new factors modulate plasma lipid levels keep providing interesting opportunities to rationally design novel therapies to treat cardiovascular disease but also metabolic disorders.

High-density lipoprotein metabolism and reverse cholesterol transport: strategies for raising HDL cholesterol.

A key to effective treatment of cardiovascular disease is to understand the body’s complex lipoprotein transport system. Reverse cholesterol transport (RCT) is the process of cholesterol movement from the extrahepatic tissues back to the liver. Lipoproteins containing apoA-I [high-density lipoprotein (HDL)] are key mediators in RCT, whereas non-high-density lipoproteins (non-HDL, lipoproteins containing apoB) are involved in the lipid delivery pathway. HDL particles are heterogeneous; they differ in proportion of proteins and lipids, size, shape, and charge. HDL heterogeneity is the result of the activity of several factors that assemble and remodel HDL particles in plasma: ATP-binding cassette transporter A1 (ABCA1), lecithin cholesterol acyltransferase (LCAT), cholesteryl ester transfer protein (CETP), hepatic lipase (HL), phospholipid transfer protein (PLTP), endothelial lipase (EL), and scavenger receptor class B type I (SR-BI). The RCT pathway consists of the following steps: 1. Cholesterol efflux from peripheral tissues to plasma, 2. LCAT-mediated esterification of cholesterol and remodeling of HDL particles, 3. direct pathway of HDL cholesterol delivery to the liver, and 4. indirect pathway of HDL cholesterol delivery to the liver via CETP-mediated transfer There are several established strategies for raising HDL cholesterol in humans, such as lifestyle changes; use of drugs including fibrates, statins, and niacin; and new therapeutic approaches. The therapeutic approaches include CETP inhibition, peroxisome proliferator-activated receptor (PPAR) agonists, synthetic farnesoid X receptor agonists, and gene therapy. Results of clinical trials should be awaited before further clinical management of atherosclerotic cardiovascular disease.

The association of the blood lead level and serum lipid concentrations may be modified by the genetic combination of the metallothionein 2A polymorphisms rs10636 GC and rs28366003 AA

Lead in blood can stimulate lipid oxidation in phosphatidylcholine and increase peroxidation in lipids. Metallothionein (MT) is a cysteine-rich protein that can influence the detoxification of heavy metals and scavenge oxidative stress for free radicals. One of the most expressive functional genes in humans is the MT2A gene. This study aims to determine if the association of the blood lead level and lipid biomarkers was influenced by MT2A polymorphisms. We recruited 677 participants after informed consent was obtained. All the samples collected were analyzed for lipid biomarkers and blood lead levels and were genotyped for MT2A polymorphisms by reverse transcription polymerase chain reaction. A short questionnaire collected the medical history and alcohol and cigarette consumption information. The data were used for descriptive analyses and linear regression models. The investigation revealed that lead elevated concentration increased low-density lipoprotein cholesterol and decreased high-density lipoprotein cholesterol (HDL-C) by multiple linear models. The carriers of the rs10636 GC-rs28366003 AA genetic combination may be less susceptive to lead elevated concentration on HDL-C than other types. In conclusion, the association of the blood lead level and HDL-C may be modified by the MT2A genetic combination: the rs10636 GC-rs28366003 AA genotype could play a protective role in lead elevated concentration on HDL-C in humans.

Loss of Function of GALNT2 Lowers High-Density Lipoproteins in Humans, Nonhuman Primates, and Rodents

Human genetics studies have implicated GALNT2, encoding GalNAc-T2, as a regulator of high-density lipoprotein cholesterol (HDL-C) metabolism, but themechanisms relating GALNT2 to HDL-C remain unclear. We investigated the impact of homozygous GALNT2 deficiency on HDL-C in humans and mammalian models. We identified two humans homozygous for loss-of-function mutations in GALNT2 who demonstrated low HDL-C. We also found that GALNT2 loss of function in mice, rats, and nonhuman primates decreased HDL-C. O-glycoproteomics studies of a human GALNT2-deficient subject validated ANGPTL3 and ApoC-III as GalNAc-T2 targets. Additional glycoproteomics in rodents identified targets influencing HDL-C, including phospholipid transfer protein (PLTP). GALNT2 deficiency reduced plasma PLTP activity in humans and rodents, and in mice this was rescued by reconstitution of hepatic Galnt2. We also found that GALNT2 GWAS SNPs associated with reduced HDL-C also correlate with lower hepatic GALNT2 expression. These results posit GALNT2 as a direct modulator of HDL metabolism across mammals.

Abstract 198: HDL Function and Genetic Regulation in a Nonhuman Primate Model of HDL Cholesterol Extremes

Recent data indicate that HDL function has effects independent of HDL cholesterol (HDL-C) levels that better predict cardiovascular risk. We aimed to characterize sterol efflux across a wide range of HDL-C, and to identify genetic determinants for both traits in a non-human primate model. To do this, we took advantage of rhesus macaque families that display spontaneous, extreme variation in HDL-C (range 13-106 mg/dL), but have total cholesterol, LDL-C, and triglyceride levels considered normal in humans. We hypothesized that genetic regulation of HDL metabolism is conserved between macaques and humans, and that sterol efflux is independent of HDL-C across the observed range of HDL-C values. We selected 16 macaque half-sib pairs matched for age-class and sex, based on maximum differences in HDL-C characterized in a larger sample (n=193), and conducted deep sequencing of exons and regulatory regions. We assessed predicted function for all variants in macaques found at 23 genes that regulate reverse cholesterol transport or are associated with HDL-C in humans, and that share ~93% identity with the corresponding human proteins. We assessed sterol efflux using J774 macrophages labeled with [ 3 H]cholesterol and stimulated with a cAMP analogue in 16 sequenced macaques, plus 6 macaques selected from the &lt;5 th /&gt;95 th percentiles of HDL-C (n=22). We found 27 predicted functional variants located at regulatory or coding regions in macaques that were within 10 bp of known variants in humans associated with HDL-C levels, coded protein deficiencies, or familial alpha-dyslipoproteinemias. Further, we show that 4 of these variants in CETP , LCAT , and ABCA1 are expected to inhibit normal protein function, as indicated by in silico prediction of changes in protein folding. Within these families, correlation between HDL-C and sterol efflux was 0.78 (P=1.65 X 10 -5 ), suggesting that a significant portion of the variation in efflux capacity cannot be accounted for by HDL-C levels. We conclude that functional genetic variation in pathways of HDL metabolism is conserved between humans and macaques, and is likely to influence both HDL-C and efflux capacity. However, a significant proportion of efflux capacity operates independently of HDL-C.

Novel natural food colourant G8000 benefits LDL- and HDL-cholesterol in humans

The aim of this study was to investigate the phenolic composition of a natural food colourant (G8000™) as well as its effects on plasma markers after 28-day consumption by healthy individuals at a dietary dose (70 g). Parameters of total cholesterol and its fractions, triglycerides and plasma enzymes biomarkers of muscle injury were measured. Major compounds identified in G8000™ by ESI-MS showed the presence of anthocyanins, organic acids, phenolic acids as well as monosaccharides. HDL levels significantly increased from 43 ± 10.2 mg/dL to 95 ± 16.9 mg/dL. LDL levels significantly decreased from 110 ± 40.9 mg/dL to 69 ± 39 mg/dL (p < 0.001). No significant statistical differences (p > 0.05) were observed for total cholesterol, triglycerides and VLDL. After the intake, plasma enzyme CK-MB decreased from 20 ± 12.1 U/L to 10 ± 1.9 U/L while LDH levels increased from 275 ± 124.4 U/L to 317 ± 114.7 U/L (p < 0.005). No significant differences were observed for CK levels. Taken together, dietary intake of natural colourant G8000™ was able to exert beneficial effects on atherosclerosis biomarkers.

Identification of four novel genes contributing to familial elevated plasma HDL cholesterol in humans

While genetic determinants strongly influence HDL cholesterol (HDLc) levels, most genetic causes underlying variation in HDLc remain unknown. We aimed to identify novel rare mutations with large effects in candidate genes contributing to extreme HDLc in humans, utilizing family-based Mendelian genetics. We performed next-generation sequencing of 456 candidate HDLc-regulating genes in 200 unrelated probands with extremely low (≤10th percentile) or high (≥90th percentile) HDLc. Probands were excluded if known mutations existed in the established HDLc-regulating genes ABCA1, APOA1, LCAT, cholesteryl ester transfer protein (CETP), endothelial lipase (LIPG), and UDP-N-acetyl-α-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase 2 (GALNT2). We identified 93 novel coding or splice-site variants in 72 candidate genes. Each variant was genotyped in the proband's family. Family-based association analyses were performed for variants with sufficient power to detect significance at P < 0.05 with a total of 627 family members being assessed. Mutations in the genes glucokinase regulatory protein (GCKR), RNase L (RNASEL), leukocyte immunoglobulin-like receptor 3 (LILRA3), and dynein axonemal heavy chain 10 (DNAH10) segregated with elevated HDLc levels in families, while no mutations associated with low HDLc. Taken together, we have identified mutations in four novel genes that may play a role in regulating HDLc levels in humans.

Apolipoprotein A-I mimetics.

To summarize recent publications in the field of apolipoprotein mimetics. Apolipoprotein mimetic peptides continue to show efficacy in a number of animal models of disease and demonstrate properties that make them attractive as potential therapeutic agents. A number of new apolipoprotein mimetics have been described recently. A major site of action of apolipoprotein mimetic peptides was found to be in the small intestine in which they decrease the levels of proinflammatory bioactive lipids. A major problem related to the use of apolipoprotein mimetic peptides is their cost, particularly those that need to be generated by solid phase synthesis with chemical addition of end-blocking groups. Novel approaches to apolipoprotein mimetic therapy have emerged recently that show promise in overcoming these barriers. Despite the recent failure of therapies designed to raise HDL-cholesterol in humans, an approach to therapy using mimetics of HDL and its components continues to show promise.

Increased risk of premature coronary artery disease in Egyptians with ABCA1 (R219K), CETP (TaqIB), and LCAT (4886C/T) genes polymorphism.

Epidemiological studies have shown a strong inverse relationship between high-density lipoprotein (HDL) cholesterol (HDLc) levels and coronary artery disease (CAD), and a low concentration of plasma HDLc is considered an independent risk factor for premature atherosclerosis. Mutations in ATP-binding cassette A1 transporter (ABCA1), cholesteryl ester transfer protein (CETP), and lecithin: cholesterol acyltransferase (LCAT) reduce HDLc in humans. To date, no study had tested the association between these polymorphisms and premature CAD (PCAD) in the Egyptian population. Here we searched for ABCA1 (rs2230806), CETP (rs708272), and LCAT (rs5923) mutations in the Egyptian population and investigated the possible association between these gene polymorphisms and PCAD. We aimed to investigate the association between ABCA1, CETP, and LCAT gene polymorphisms and PCAD in Egyptians. A total of 235 Egyptians-116 with documented PCAD (PCAD group) and 119 controls-were enrolled in the study. Mutation carriers with low HDLc had an elevated risk of PCAD (odds ratio [OR] = 11.38 for ABCA1 mutation carriers, P = .000; OR = 5.41 for CETP mutation carriers, P = .000; OR = 5.92 for LCAT mutation carriers, P = .000). Moreover, mutations in ABCA1, CETP, and LCAT were significantly associated with hyperlipidemia in this study. These observations show that the R allele of ABCA1, the B1 allele of CETP, and the T allele LCAT genes are associated with PCAD in Egyptians. They have more considerable effect on patients with low HDLc.

Erratum

Clinical GeneticsVolume 80, Issue 4 p. 406-406 Free Access Erratum This article corrects the following: Novel mutations in scavenger receptor BI associated with high HDL cholesterol in humans LR Brunham, I Tietjen, AE Bochem, RR Singaraja, PL Franchini, C Radomski, M Mattice, A Legendre, GK Hovingh, JJP Kastelein, MR Hayden, Volume 79Issue 6Clinical Genetics pages: 575-581 First Published online: May 5, 2011 First published: 08 September 2011 https://doi.org/10.1111/j.1399-0004.2011.01766.xAboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Novel mutations in scavenger receptor BI associated with high HDL cholesterol in humans In the second sentence of the results section, the sentence: “We identified two novel missense mutations, S112F (nucleotide C588T) and T175A (nucleotide A776T),…” should read as, “We identified two novel missense mutations, S112F (nucleotide C588T) and T175A (nucleotide A776G),…”, that is, the letter “T” after number 776 should appear as the letter “G”. Reference 1 Brunham LR, Tietjen I, Bochem AE et al. Novel mutations in scavenger receptor BI associated with high HDL cholesterol in humans. Clin Genet 2011: 79: 575– 581. Wiley Online LibraryCASPubMedWeb of Science®Google Scholar Volume80, Issue4October 2011Pages 406-406 ReferencesRelatedInformation

Novel mutations in scavenger receptor BI associated with high HDL cholesterol in humans

The scavenger receptor class B, member 1 (SR-BI), is a key cellular receptor for high-density lipoprotein (HDL) in mice, but its relevance to human physiology has not been well established. Recently a family was reported with a mutation in the gene encoding SR-BI and high HDL cholesterol (HDL-C). Here we report two additional individuals with extremely high HDL-C (greater than the 90th percentile for age and gender) with rare mutations in the gene encoding SR-BI. These mutations segregate with high HDL-C in family members of each proband and are associated with a 37% increase in plasma HDL-C in heterozygous individuals carrying them. Both mutations occur at highly conserved positions in the large extracellular loop region of SR-BI and are predicted to impair the function of the SR-BI protein. Our findings, combined with the prior report of a single mutation in the gene encoding SR-BI, further validate that mutations in SR-BI are a rare but recurring cause of elevated HDL-C in humans.

Plasma apolipoprotein M responses to statin and fibrate administration in type 2 diabetes mellitus

Purpose Plasma apolipoprotein M (apoM) is potentially anti-atherogenic, and has been found to be associated positively with plasma total, LDL and HDL cholesterol in humans. ApoM may, therefore, be intricately related to cholesterol metabolism. Here, we determined whether plasma apoM is affected by statin or fibrate administration in patients with diabetes mellitus. Methods Fourteen type 2 diabetic patients participated in a placebo-controlled crossover study which included three 8-week treatment periods with simvastatin (40 mg daily), bezafibrate (400 mg daily), and their combination. Results ApoM was decreased by 7% in response to simvastatin ( P < 0.05 from baseline and placebo), and remained unchanged during bezafibrate and combined simvastatin + bezafibrate administration. Plasma apoM concentrations correlated positively with apoB-containing lipoprotein measures at baseline and during placebo ( P < 0.02 to P < 0.001), but these relationships were lost during all lipid lowering treatment periods. Conclusions This study suggests that, even though plasma apoM is lowered by statins, apoM metabolism is to a considerable extent independent of statin- and fibrate-affected pathways involved in cholesterol homeostasis.

Effect of Animal and Industrial Trans Fatty Acids on HDL and LDL Cholesterol Levels in Humans – A Quantitative Review

Background Trans fatty acids are produced either by industrial hydrogenation or by biohydrogenation in the rumens of cows and sheep. Industrial trans fatty acids lower HDL cholesterol, raise LDL cholesterol, and increase the risk of coronary heart disease. The effects of conjugated linoleic acid and trans fatty acids from ruminant animals are less clear. We reviewed the literature, estimated the effects trans fatty acids from ruminant sources and of conjugated trans linoleic acid (CLA) on blood lipoproteins, and compared these with industrial trans fatty acids.Methodology/Principal FindingsWe searched Medline and scanned reference lists for intervention trials that reported effects of industrial trans fatty acids, ruminant trans fatty acids or conjugated linoleic acid on LDL and HDL cholesterol in humans. The 39 studies that met our criteria provided results of 29 treatments with industrial trans fatty acids, 6 with ruminant trans fatty acids and 17 with CLA. Control treatments differed between studies; to enable comparison between studies we recalculated for each study what the effect of trans fatty acids on lipoprotein would be if they isocalorically replaced cis mono unsaturated fatty acids. In linear regression analysis the plasma LDL to HDL cholesterol ratio increased by 0.055 (95%CI 0.044–0.066) for each % of dietary energy from industrial trans fatty acids replacing cis monounsaturated fatty acids The increase in the LDL to HDL ratio for each % of energy was 0.038 (95%CI 0.012–0.065) for ruminant trans fatty acids, and 0.043 (95% CI 0.012–0.074) for conjugated linoleic acid (p = 0.99 for difference between CLA and industrial trans fatty acids; p = 0.37 for ruminant versus industrial trans fatty acids).Conclusions/SignificancePublished data suggest that all fatty acids with a double bond in the trans configuration raise the ratio of plasma LDL to HDL cholesterol.

Loss-of-function variants in endothelial lipase are a cause of elevated HDL cholesterol in humans

Elevated plasma concentrations of HDL cholesterol (HDL-C) are associated with protection from atherosclerotic cardiovascular disease. Animal models indicate that decreased expression of endothelial lipase (LIPG) is inversely associated with HDL-C levels, and genome-wide association studies have identified LIPG variants as being associated with HDL-C levels in humans. We hypothesized that loss-of-function mutations in LIPG may result in elevated HDL-C and therefore performed deep resequencing of LIPG exons in cases with elevated HDL-C levels and controls with decreased HDL-C levels. We identified a significant excess of nonsynonymous LIPG variants unique to cases with elevated HDL-C. In vitro lipase activity assays demonstrated that these variants significantly decreased endothelial lipase activity. In addition, a meta-analysis across 5 cohorts demonstrated that the low-frequency Asn396Ser variant is significantly associated with increased HDL-C, while the common Thr111Ile variant is not. Functional analysis confirmed that the Asn396Ser variant has significantly decreased lipase activity both in vitro and in vivo, while the Thr111Ile variant has normal lipase activity. Our results establish that loss-of-function mutations in LIPG lead to increased HDL-C levels and support the idea that inhibition of endothelial lipase may be an effective mechanism to raise HDL-C.

Abstract 1693: Effect of Pitavastatin on Serum Concentrations of Endothelial Lipase and High-Density Lipoprotein Cholesterol in Humans

[Purpose] Endothelial lipase (EL) is a novel phospholipase which regulates serum high-density lipoprotein cholesterol (HDL-C) levels. In the present study, we have measured serum levels of EL in human subjects, and examined the effect of statins on serum HDL levels and EL mass. [Methods and Results] A sandwich ELISA for human EL was established using two monoclonal antibodies against amino- or carboxy-terminus of human EL. Serum EL concentrations were measured and compared with the serum lipid profile in 237 patients with cardiovascular diseases. There was no significant correlation between serum EL mass and age or gender. Serum EL levels were negatively associated with serum HDL-C levels, but not with serum LDL-C, total cholesterol, or triglyceride levels. Forty-eight patients with hypercholesterolemia were treated with pitavastatin for 6 months, and serum EL mass was evaluated before and after the pitavastatin treatment. Pitavastatin treatment significantly reduced serum EL levels by 15% and increased HDL-C levels by 12%. Complimentary cell culture experiments revealed that pitavastatin suppressed basal and cytokine-induced EL expression and phospholipase activities in endothelial cells, which is reversed by the concomitant treatment with mevalonate or geranylgeranylpyrophosphate. Also, overexpression of RhoA T19N, a dominant negative mutant of RhoA, decreased the EL expression. [Conclusion] EL is a determinant of serum HDL-C levels in humans. Pitavastatin reduced EL expression through the protein isoprenylation and inhibition of Rho activity, and raised serum HDL-C levels. Thus, EL would be a target molecule for the HDL-raising pharmaceutical interventions.